Using morphological and biochemical procedures, we proposed to determine the effects of retinoids on the structural and functional differentiation of the mammary gland both in vivo and in vitro. In addition, retinoid effects on the development of carcinogen induced hyperplastic alveolar nodule like structure in vitro and their potential to develop tumors upon subsequent transplantation is also proposed. Furthermore, extensive characterization of retinoic acid binding protein in normal and neoplastic mammary tissues will also be made and retinoid receptor levels will be correlated with estradiol receptors in respective tissues. Investigations will be made to determine the effects of retinoids on serum prolactin levels. Finally, it is proposed that the validity of the evident mechanism(s) by which retinoids act will be examined in vivo.